1. Field of the Invention
The present invention relates to a picture-synthetic system for decoding, synthesizing, and reproducing picture data compressed by a MPEG (Moving Picture Experts Group) system and subordinate picture data such as movie or karaoke subtitles compressed by a run-length system, and a picture-synthetic method therefor.
2. Description of the Related Art
In a conventional system for decoding, synthesizing, and reproducing picture data compressed by a MPEG system and subordinate picture data such as movie or karaoke subtitles compressed by a run-length system, the processing of decoding and synthesizing the data are performed by the use of software.
However, in the conventional system, there exists a problem that, when the processing of decoding and synthesizing the data are performed by the use of software, a load on a CPU used for the computation by synthesizing the subordinate picture data on the main picture data is increased and hence the CPU becomes deficient in its capacity for outputting the main picture in real time, which increases the number of omitted frames.
It is the object of the present invention to provide a picture-synthetic system which can reduce a load on a CPU for synthesizing a still picture such as movie or karaoke subtitles on a moving picture and a picture-synthetic method therefor.
A picture-synthetic system according to the present invention comprises a memory device, a data-separating section, a picture-decoding section, a subordinate-picture-decoding section, a subordinate-picture-data-converting section, and a picture-synthetic section, wherein the memory device has means for memorizing multiplex data of picture data compressed and encoded by a MPEG system and subordinate picture data compressed and encoded by a run-length system; the data-separating section has means for separating the picture data compressed and encoded by the MPEG system and the subordinate picture data compressed and encoded by the run-length system from the multiplex data read out of the memory device and for outputting the picture data compressed and encoded by the MPEG system to the picture-decoding section and the subordinate picture data compressed and encoded by the run-length system to the subordinate-picture-decoding section; the picture-decoding section has means for decoding the picture data compressed and encoded by the MPEG system and for outputting the MPEG-decoded data to the picture-synthetic section; the subordinate-picture-decoding section has means for decoding the subordinate picture data compressed and encoded by the run-length system and for outputting the run-length-decoded data to the subordinate-picture-data-converting section; the subordinate-picture-data-converting section has a data-format-converting section for converting a format of the run-length-decoded data, a redundant-pixel-removing section for removing the redundant pixels of the run-length-decoded data, and means for outputting the converted data to the picture-synthetic section; and the picture-synthetic section has means for synthesizing the converted data received from the subordinate-picture-decoding section on the MPEG-decoded data received from the picture-decoding section in the form of YUV to display.
Further, the data-format-converting section may have means for converting the run-length-decoded data into 8-bit data which indicates a color index value and a contrast value per pixel.
Still further, the redundant-pixel-removing section may have means for changing a display position to a main picture and for outputting to the picture-synthetic section only the rectangular region which includes the effective pixels of the run-length-decoded data, in the case where a region of redundant pixels whose contrast values are all xe2x80x9c0xe2x80x9d exists outside the rectangular region which includes the effective pixels of the run-length-decoded data.
A picture-synthetic method for the picture-synthetic system according to the present invention comprises the steps of; memorizing multiplex data of the picture data compressed and encoded by the MPEG system and the subordinate picture data compressed and encoded by the run-length system in the memory device; separating the picture data compressed and encoded by the MPEG system and the subordinate picture data compressed and encoded by the run-length system from the multiplex data read out of the memory device and outputting the picture data compressed and encoded by the MPEG system to the picture-decoding section and the subordinate picture data compressed and encoded by the run-length system to the subordinate-picture-decoding section in the data-separating section; decoding the picture data compressed and encoded by the MPEG system and outputting the MPEG-decoded data to the picture-synthetic section in the picture-decoding section; decoding the subordinate picture data compressed and encoded by the run-length system and outputting the run-length-decoded data to the subordinate-picture-data-converting section in the subordinate-picture-decoding section; converting a format of the run-length-decoded data by the data-format-converting section and removing the redundant pixels of the run-length-decoded data by the redundant-pixel-removing section, and outputting the converted data to the picture-synthetic section in the subordinate-picture-data-converting section; and synthesizing the converted data received from the subordinate-picture-data-converting section on the MPEG-decoded data received from the picture-decoding section in the form of YUV to display in the picture-synthetic section.
Further, a picture-synthetic method for the picture-synthetic system according to the present invention may comprise the step of converting the run-length-decoded data into 8-bit data which indicates a color index value and a contrast value per pixel in the data-format-converting section.
Still further, a picture-synthetic method for the picture-synthetic system according to the present invention may comprise the step of changing a display position to a main picture and outputting only the rectangular region which includes the effective pixels of the run-length-decoded data to the picture-synthetic section in the redundant-pixel-removing section, in the case where a region of redundant pixels whose contrast values are all xe2x80x9c0xe2x80x9d exists outside the rectangular region which includes the effective pixels of the run-length-decoded data.
The present invention provides synthesizing means for reducing a processing load when the subordinate picture data is synthesized on the picture data in the picture-synthetic system for decoding, synthesizing, and reproducing the picture data compressed and encoded by the MPEG system and the subordinate picture data, such as movie or karaoke subtitles, compressed and encoded by the run-length system, and the picture-synthetic method therefor.
The memory device memorizes the multiplex data of the compressed picture data and the compressed subordinate picture data. The data-separating section separates the subordinate picture data and the subordinate-picture-decoding section decodes the separated subordinate picture data into the run-length-decoded-data. The subordinate-picture-data-converting section changes the format of the decoded subordinate picture data to reduce the number of table-looking-up operations required for a process of synthesizing and removes the redundant pixel data which is included in the decoded subordinate picture data and whose contrast values are zero and hence which can not be seen even if synthesized. The picture-synthetic section synthesizes the subordinate picture data converted by the subordinate-picture-data-converting section on the main picture at the designated synthesizing positions.
In this way, the load of the picture-synthetic section when the subordinate picture data is synthesized on the main picture can be reduced by converting the subordinate picture data which is decoded by the run-length system in the subordinate-picture-converting section.